Method of and apparatus for monitoring of muscle activity

ABSTRACT

Apparatus for monitoring muscle activity, said apparatus comprising means for providing signals indicative of muscle activity, for example EMG-signals, means for processing of said signals in order to detect a particular activity and means for providing a feedback signal, wherein said device is designed in order to be individually adaptable in a set-up mode. The apparatus can be used for detecting and prevention of undesired activities such as bruxism, movements that are damaging or unwanted etc. The detection can be performed with great certainty since the individual parameters of the user are utilized for laying down reference values, threshold values, criteria for triggering of feedback signals, etc., which may take place at a set-up procedure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.10/552,366 filed Oct. 3, 2005, now U.S. Pat. No. 8,160,689, which is a371 of PCT/DK2004/000223 filed Mar. 31, 2004, which claims priority ofDanish Patent Application PA 2003 00500 filed Apr. 1, 2003.

FIELD OF THE INVENTION

The invention relates to an apparatus for monitoring muscle activity.Further, the invention relates to a method of monitoring muscleactivity. Further, the invention relates to a method of setting up anapparatus according to the invention. The invention also pertains touses of such a device and/or such a method.

BACKGROUND OF THE INVENTION

In a number of circumstances it is desirable to be able to monitormuscle activities of especially human beings, in particular with theobjective of being able to detect and possibly avoid undesirable,unnecessary and/or potentially harmful muscle activities. In particularit is desirable to be able to detect such muscle activities with theobjective of being able to interfere in such a manner that theundesirable activity may be limited or even brought to an end.

Examples of such situations are for example work situations wheremuscles are used incorrectly whereby irritation, pain or even damage mayoccur. This also relates to circumstances where muscles are strainedduring work stress and/or where person suffer from pain in the back ofthe head and shoulder caused by incorrect work position. Examples ofthis may be monotonous work (RSI—Repetitive Strain Injury;CTD—Cumulative Trauma Disorders; CTS—Carpal Tunnel Syndrome), work at aPC-station, (e.g. computer mouse overuse syndrome), office work(incorrect sitting) etc.

Also muscle activities may be concerned, which are brought about more orless consciously or even completely unaware, for example in the sleep,and which may also cause damage or unwanted effects.

As an example of such undesired muscular activities reference may bemade to the affliction bruxism that in general is defined as powerfuljaw movements without any real function and which takes the form ofinvoluntary grinding movements of the teeth during strong clenching.This affliction may cause serious dental damages such as for examplewearing of the teeth, damages to lips and the tongue, lose teeth,gingival pockets etc. Bruxism is often in addition also associated withpain in the back of the head and chronic headache.

Bruxism is normally divided into chronic and acute bruxism. Acutebruxism can happen to all and may often be observed in stresssituations, for example at athletes in games or at persons that have toobserve a deadline. Chronic bruxism is divided into nocturnal anddaytime bruxism. Daytime bruxism is characterized by being a consciousclenching of upper and lower jaws and grinding of the teeth, althoughdominated by the latter. Since night-time bruxism is unconscious it maynormally only be perceived by the surroundings (for example relations)as an unpleasant squeaky noise. The daytime bruxism may often beprovoked by exposing the patient to stress. This daytime bruxism may beperceived as a bad habit. This form of the affliction may be relievedrelatively easy by drawing the attention of the person to the bruxism.As regards night-time bruxism the problem is more complex since it isdifficult to distinguish between bruxism events and ordinary muscleactivity. It is noted, though, that bruxism typically lasts more than2-5 seconds. This nocturnal form of the suffering is often alleviated byprotecting the teeth with a splint.

U.S. Pat. No. 4,669,477 discloses an apparatus for treatment of bruxism.This apparatus is based on that the muscle activity in the jaw musclesof a patient can be sensed and compared with a threshold value that maybe adjusted. If the sensed muscle activity exceeds the threshold value astimulation signal is generated. The stimulation signal is applied tothe jaw muscle by means of electrodes. In an embodiment of thisapparatus the stimulation signal comprises a start region, where theintensity of the signal may be increased gradually, a stimulation regionwhere the intensity is constant, and a termination region where theintensity of the signal decreases gradually.

It is however a problem that the apparatus uncritically triggers astimulation when the threshold value is exceeded. It turns out that longtime use of the apparatus has a preventive effect and that bruxism thusmay be avoided without using the apparatus. The patient learnsunconsciously that he/she must not grind the teeth. This is primarilycaused by that when using the apparatus the patient is punished withsmall electric shocks in the form of the stimulation signal when themuscle activity exceeds the threshold value. Since a typical person thatmay or may not suffer from bruxism has a considerable muscle activity inthe jaw region caused by dreaming, which activity may have the samelevel as real bruxism, a considerable number of stimulations of the jawmuscle will be triggered during normal sleep when the apparatus is used.With reference to the above-mentioned effect that the patient learnsfrom the punishment he/she receives in the form of small electric shocksthere is a considerable danger that the patient similarly is punishedfor the normal and natural jaw activity that takes place during sleep.This natural jaw activity may prove to be important for the dreams aperson has during sleep.

From U.S. Pat. No. 6,093,158 A there is further known a system fortreatment of inter alia bruxism. This document describes an apparatusthat may be wholly inserted in the ear canal in the same manner as anhearing aid (ITE heraring aid) and where by means of a microphone soundsmay be picked-up in the ear, which sounds may possibly stem from teethgrinding. By means of a processor it is investigated whether criteriafor detection of bruxism are fulfilled where after a sound signal may betransmitted by means of a transducer as a stimulation to the user.

The criteria for detection of bruxism may be exceeding of a sound levelthat can be adjusted by the user. Other criteria such as the number ofevents pr. unit of time and the duration are generally mentioned.Besides from this the signal processing itself is not further described.The document mentions various options regarding detection, e.g. by meansof sound sensors, microphones, EMG (Electromyographic) electrodes etc.and feedback options, for example with sound.

In an embodiment the apparatus may detect small changes in the structureof an ear by means of a transmitter and a receiver for example if theuser begins grinding of the teeth. This embodiment has the flaw that thechanges may possibly be quite normal jaw movements that may not besynonymous with teeth grinding. The apparatus may therefore perceivethese muscle activities as undesired muscle contractions in the form ofteeth grinding and thus activate the feedback

In another embodiment the sound is measured in the ear, which sound maystem from grinding or snoring. No criteria are mentioned for how thesesound signals/sources are differentiated from each other. This prior artsystem functions in the manner that a threshold value is adjusted and ifthis threshold value is exceeded the feedback will be activated. Thismeans that if the user for example coughs, talks in his/her sleep orgenerates a normal sound during sleep, this will cause an exceeding ofthe threshold value and thus the patient will receive an undesiredfeedback.

Further an embodiment comprises additional sound sensors that may beplaced at various locations on the face. If the microphone placed in theear cannot detect the sound via the ear canal these sensors will be ableto detect the sound that may inter alia stem from teeth grinding orsnoring. Hereby the disadvantage will again arise that the sound sourcecan be anything that uncritically will activate the feedback if thethreshold value is exceeded.

In this prior art document it is also mentioned that e.g. other types ofsensors may be placed in the mouth of the user. A sound source for useas feedback may also be placed on the body of the user or at the side ofthe bed. The feedback may possibly be activated in the form of avibrator placed on a location on the body.

In the document it is thus mentioned that a stimulation feedback may beused but no explanation has been given as to how such a stimulation isactivated and which criteria must be fulfilled besides exceeding of thethreshold value. It is thus not explained which properties thestimulation should have.

As mentioned this known system will have the drawback that normalbite-activities, sounds, movements etc. during sleep may cause anactivation of the feedback, since steps have not been taken todifferentiate between these. Further, considerations have not been takenas regards the influence via the sensors from other external sources. Itis thus also a general drawback that the apparatus will uncriticallytrigger a feedback when the threshold value is exceeded.

Finally it may be mentioned that in regard to such a prior art apparatusthere will be a risk that the user is wakened during sleep, inter aliacaused by feedback in situations that are not related to bruxism. Thismay have the disadvantage that the sleep rhythm is disturbed which willstress the user further, which again may worsen the bruxism of the user,since stress is an essential cause of bruxism.

It is thus an objective of the invention to provide an apparatus for anda method of monitoring of bruxism, by means of which these drawbacks arealleviated.

It is thus in particular an objective of the invention to provide suchan apparatus and such a method, by means which an individual adaptationto the user may be achieved.

Further, it is an objective of the invention to provide such anapparatus and such a method by means of which considerations may betaken in regard to normal movements and/or sounds made during sleep thatthe user does not have to be “punished” for, i.e. meaning that nofeedback signal will be emitted in such situations.

Additionally it is an objective of the invention to provide such anapparatus and such a method whereby it is seen to it that the usershould not be awakened when the feedback is activated as a sound or avibration etc.

It is even further an objective of the invention to provide suchapparatuses and such methods that will reduce or even prevent thedisadvantage that the sleep rhythm of the user is disturbed because oferroneously triggered feedback signals, whereby the sleep rhythm of theuser as far as possible will not be disturbed.

Finally it is an objective of the invention to provide an apparatus forand a method of monitoring of muscle activities that may be used notonly for monitoring with a view to detection of bruxism but also in avariety of other situations where it is desirable to be able to detectinopportune or of other reasons undesired muscle activities, whereby theattention of an individual may be brought to this by means of a feedbacksignal.

These and other objectives are achieved by the invention as explained infurther detail in the following.

SUMMARY OF THE INVENTION

The invention relates to an apparatus for monitoring of muscle activity,said apparatus comprising

means for providing signals indicative of muscle activity, for exampleEMG-signals,

means for processing of said signals in order to detect a particularactivity,

means for providing a feedback signal,

wherein said device is designed in order to be individually adaptable ina set-up node.

Hereby it is achieved that the apparatus in accordance with theinvention can be used for detecting and prevention of undesiredactivities such as bruxism, movements that are damaging or unwanted etc,as the detection can be performed with great certainty since theindividual parameters of the user are utilized for laying down referencevalues, threshold values, criteria for triggering of feedback signalsetc., which may take place at a special set-up procedure.

Expediently, said apparatus may be designed with means for sensing andregistering of a normally occurring muscle activity.

Hereby it is achieved that the apparatus will be aware of said normallyoccurring muscle activity that may be utilized as a reference value whenlaying down criteria for triggering of a feedback signal, whereby thedanger of having an erroneous feedback can be reduced or even preventedcompletely.

In accordance with a particular expedient embodiment, said apparatus maybe designed with means for sensing and registering of an essentiallymaximal muscle activity, for example a maximal jaw clenching activity.

Hereby it is achieved that that a measure is registered corresponding tothe level of the muscle activity, e.g. the chewing force for the user inquestion, whereby this level may be taken into consideration when layingdown criteria for triggering of a feedback signal. Hereby, an unseenhigh degree of user friendliness may be achieved.

In accordance with a further expedient embodiment, said apparatus may bedesigned for sensing and registering of muscle activity during one ormore predefined normally occurring muscle activities, such as one ormore grimaces.

Hereby it is achieved that muscle activities that may be expected tooccur normally, are registered by the apparatus, which may be utilizedwhen laying down criteria for triggering, whereby these normallyoccurring activities can not in them selves trigger a feedback signal.

In accordance with a further expedient embodiment, as specified in claim5, said apparatus may comprise means for registering and storing muscleactivity during a time interval.

Hereby it is achieved that the level of activity and possibly patternsof activity can be registered while the user is wearing the apparatus,for example for a relatively long period and/or for several periods oftime, whereby reference values etc. can be established with a higherdegree of certainty and accuracy. Thus, also criteria for triggering thefeedback may be established with greater certainty and accuracy.

Advantageously, said apparatus may be designed to be individuallyadaptable by having means for adjusting said feedback signal.

Hereby it is achieved that that the individual user may adjust and setthe feedback signal, e.g. a vibration, an electric signal, or anotherform of stimulus to a level that will be suitable to the user, e.g. alevel that will not be uncomfortable to the user but that may clearly besensed/felt/heard etc.

In accordance with a particular expedient embodiment, said means forprocessing of said signals in order to detect a particular activity maycomprise means for pattern recognition, e.g. using FFT (Fast FourierTransform) analysis.

Hereby an even higher degree of certainty is achieved when detectingundesired muscle activities since patterns of activity registered inadvance can be utilized for establishing criteria for triggering offeedback.

Expediently, said means for providing signals indicative of muscleactivity may comprise one or more electrodes for sensing of EMG-signals.

Hereby it is achieved that said muscle activities can be sensed andregistered in a certain and advantageous manner.

Advantageously, said means for providing signals indicative of muscleactivity may comprise one or more electrodes for sensing of EEG-signals(Electroneurographic signals).

Hereby a further increased certainty may be achieved when a feedbacksignal is triggered since said EEG signals can provide furtherinformation for establishing of criteria for triggering. For examplewhen bruxism is concerned where it is known that bruxism in most casesoccurs in certain phases of sleep that may be detected by means of EEGsignals.

In accordance with a further advantageous embodiment, said apparatus maycomprise means for testing of said electrodes and in particular theconnectivity to the user by supplying a test voltage to theelectrode(s), possibly as a superimposed voltage, measuring of aresulting signal and comparing the resulting current with referencevalue(s).

Hereby it can be assured that e.g. the user has placed the electrodes insuch a manner that the resistance to the skin is below a certain valuethat allows the apparatus to perform without flaws. In this manner theuser may initially be confirmed that the apparatus is operational whenthe user has placed the apparatus e.g. on the forehead and further, theelectrode connectivity may be monitored periodically or continuouslywhereby it is detected if the connectivity falls below the prescribedrange, in which case the user may be alerted and/or the operation of theapparatus may be stopped, possibly temporarily.

Preferably, said means for providing signals indicative of muscleactivity may comprise a microphone, a sensor for sensing of vibrationsand/or other sensor means.

Hereby it is achieved that that signals may be registered in variousmanners that may be adapted to the particular purpose and that furthercombinations of such means may be used.

In accordance with a further advantageous embodiment, said apparatus maycomprise means for storing data corresponding to measured and/orprocessed signals.

Hereby it is achieved that data corresponding to a number of sessions,e.g. nights, may be preserved and used for e.g. statistical purposes andfor assessing the improvement of e.g. user behaviour, bruxism eventsetc. and possibly for redefining the settings of the apparatus, forexample when the user returns to a supervisor or the like.

Preferably, the apparatus may comprise means for transferring storeddata to a computer, e.g. a PC or the like, which may take place at asupervisor or at the user's own PC.

Further, such data may be sent via the Internet to e.g. a supervisor forevaluation and use.

In accordance with a still further advantageous embodiment, saidapparatus may be operated in a set-up mode and a use-mode, that in saidset-up mode individual reference signals, signals corresponding tospecific individual muscle activities and individual bio-feedback signalcharacteristics may be set-up, and that in said user mode the device maymonitor muscle activity and provide bio-feedback in accordance withpredefined rules and settings.

Hereby, the settings of the apparatus may be established in anadvantageous manner. For example may the setting up be performed undersupervision of a skilled and trained person, e.g. a supervisor, adentist or the like that may lead the potential user through theprocedure and may assure that the setup is performed successfully. Afterthe setup procedure has been performed, the supervisor may put theapparatus in the use-mode, whereby the apparatus may be operated safelyand in an uncomplicated manner by the user.

According to a preferable embodiment said apparatus may comprise a usermodule for wearing on the head, e.g. on the forehead, on or in the ear,etc.

Hereby it is achieved that that apparatus may be designed conveniently,e.g. with electrodes that may readily monitor e.g. the muscleTemporalis, and in such a manner that the apparatus may be locatedunobtrusively, which will be preferable if the apparatus is to be wornduring sleep.

According to a further advantageous embodiment, said device may comprisea slave module and a master module, said slave module being designed forwearing by a human being.

Hereby it is achieved that the part that has to be worn by the user maybe miniaturized as much as possible since components for e.g. signalprocessing etc. may be placed in the master module.

Preferably, said apparatus may comprise charging means, e.g. for saiduser module or for said slave module.

According to a particularly advantageous embodiment, said apparatus maycomprise means for indicating operating steps to a user such as visualmeans, e.g. a LED, or acoustic means.

Hereby the user may in an expedient manner receive instructionsregarding the apparatus, e.g. regarding the on/off status, regarding thelevel of the feedback when this is adjusted etc. Further it is notedthat when the apparatus is worn on the head, e.g. on the forehead, alight indicator in the form of e.g. a two- or three colour LED may beparticular advantageous since the user may be aware of the light,colour, frequency etc even when the apparatus is worn and even at night.

According to further advantageous embodiment, said apparatus maycomprise display means for displaying instructions and/or resultsstemming from a monitoring session and/or a number of sessions.

Such display means may preferably by use of words, icons etc. indicateto the user the status of the apparatus, the operational possibilitiesetc. as well as further information such as statistical data concerninglapsed sessions etc. The user may for example view the display using amirror when the apparatus is worn on the head. In this case theinformation shown on the display may be a mirror image, i.e. laterallyreserved for the user's convenience.

The invention also relates to a method of monitoring muscle activity,said method comprising the steps of

providing signals indicative of muscle activity, for exampleEMG-signals,

processing of said signals in order to detect a particular activity,said processing of said signals taking into consideration specificindividual parameters and/or references, and providing a feedback signalin case a particular activity has been detected.

Hereby it is achieved that the method in accordance with the inventioncan be used for detecting and prevention of undesired activities such asbruxism, movements that are damaging or unwanted etc, as the detectioncan be performed with great certainty since the individual parameters ofthe user are utilized for laying down reference values, thresholdvalues, criteria for triggering of feedback signals etc., which may takeplace at a special set-up procedure

Preferably, said feedback is provided on the basis of an evaluationcomprising a maximum force calculation, an area calculation and/or apattern recognition process on the basis of a FFT-processing (FastFourier Transform).

Further, the invention also pertains to a method of setting up anapparatus, whereby an essentially maximal muscle activity such as amaximal jaw clenching is performed and the corresponding muscle activityis sensed and registered, one or more predefined muscle activitiesis/are performed, e.g. grimaces, and the corresponding muscle activityis sensed and registered, and a threshold value for outputting of afeedback-signal is adjusted.

Hereby it is achieved that the expected maximal level of activity aswell as normally occurring muscle activities may be registered by theapparatus, which may be utilized for establishing criteria for releasinga feedback to the user in such a manner that the criteria is adapted tothe user and in such a manner that the normally occurring activitiescannot trigger a feedback.

Further, the invention relates to a method of setting up an apparatus,possibly subsequent to a setting-up procedure, whereby

said method comprises the steps of using the apparatus in a set-up mode,whereby values and/or parameters corresponding to individual muscleactivities are registered and possibly stored for one or more periods oftime, and

whereby said registered and/or stored values and/or parameters areutilized for providing individual reference values for normal use of theapparatus.

Hereby the settings of the apparatus, e.g. the criteria for triggering afeedback, may be fine-tuned and adapted to a higher degree to theparticular user.

The invention also relates to use of an apparatus for preventivetreatment of bruxism.

Further, the invention relates to use of an apparatus for correctivemonitoring of human body positioning and/or movements.

Finally, the invention relates to use of an apparatus for adjusting ofhuman body positioning and/or movements during work activity.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in further detail below with referenceto the drawings of which

FIG. 1 shows an apparatus in accordance with an embodiment of theinvention, worn by a user,

FIG. 2 shows such an apparatus in an enlarged view,

FIG. 3 shows a flow diagram for a set-up procedure according to ageneral embodiment of the invention,

FIGS. 4 to 7 show different display images of an apparatus according toan embodiment of the invention,

FIG. 8 shows in block diagram form a general overview of an apparatus asillustrated in FIGS. 1 and 2,

FIG. 9 illustrates a system in accordance with a further embodiment ofthe invention in block diagram form,

FIG. 10 shows a block diagram of a signal processing method inaccordance with several embodiments of the invention,

FIG. 11 illustrates Peak Detection by means of a folding principle,

FIG. 12 illustrates signal processing performed in a master module inaccordance with a further embodiment of the invention,

FIG. 13 illustrates signal processing in a slave module according to afurther embodiment of the invention,

FIGS. 14-16 show a further embodiment of the invention comprising aslave module for placing at an ear,

FIGS. 17-21 show an even further embodiment of the invention, alsocomprising a slave module,

FIG. 22 shows a particular stimulation module, for example a vibratormodule, according to an even further embodiment of the invention,

FIG. 23 illustrates the signal processing in connection with a vibratormodule,

FIG. 24 illustrates the data processing system in a PC in accordancewith an embodiment of the invention,

FIG. 25 shows a block diagram for a further embodiment of an apparatusaccording to the invention,

FIG. 26 shows a first signal which represents muscle activity as afunction of time, where various forms of muscle activity occur,

FIG. 27 shows a second signal which represents the muscle activity as afunction of time, where an area and a RMS-value are calculated duringeach time interval (500 msec),

FIG. 28 shows a third signal, which represents muscle activity as afunction of time, where an area and a RMS-value are calculated duringmuscle activities which lie above the threshold value and last longerthan 5 seconds,

FIG. 29 shows the area below the Maximum Biting Force (MBF) in 5seconds, which is used for determining the threshold value that may varyfrom 3 to 20% of MBF,

FIG. 30 shows the EEG-signal processing procedure, which is a method foranalyzing the electric activities of a brain. These activitiescontribute primarily to potentials that may be measured on the surfaceof the scull,

FIG. 31 shows a route diagram for the measuring of muscle activity andtriggering of a stimulation signal,

FIG. 32 shows an example of a stimulation signal, and

FIGS. 33 and 34 show an embodiment of an Anti-Bruxism Module, where thisembodiment of the apparatus is placed around the neck, and where EMGelectrodes can be mounted on the jaw muscles and/or the forehead (abovethe eyes).

DETAILED DESCRIPTION OF THE INVENTION

In the following the invention will be explained in further detail withreference to a number of embodiments, of which several pertain tobruxism. It will however be understood that the invention may beutilized within a large field of applications as also stated in otherplaces herein.

FIG. 1 shows an apparatus 10 according to a preferred embodiment of theinvention for detecting and treating bruxism, e.g. for monitoring muscleactivity and for providing feedback. As illustrated the apparatus 10 isworn by a user, e.g. placed on the head with a housing 12 of theapparatus placed at the forehead and a strap 14 or the like placedaround the head. The apparatus comprises display means 16, a number ofbuttons 18, e.g. two as shown, for operating the apparatus and anindicator 20 such as an indication light, a LED or the like. The LEDindicator 20 preferably comprises a three-colour LED. It will beunderstood, however, that more than one indicator 20 may be provided,e.g. two or more LED's etc. The functions of these means and theapparatus will be explained in detail in the following.

FIG. 2 shows such an apparatus in an enlarged view. It will beunderstood that the housing 12 of the apparatus 10 in addition to theaforementioned display means 16 etc. may contain other parts such aselectronic circuitry for processing of signals etc. a microprocessor,storage means, a battery for supplying energy, etc. As indicated thedisplay means 16 may comprise a number of indicator means and features,e.g. a battery indicator 24, an electrode connection indicator 26 forindicating the level of connectivity between electrodes and the skin ofthe user, and a main display 22 that may be utilized for a number offunctions, which will be explained later on.

Further, FIG. 2 shows that the strap 14 may be equipped with anelectrode carrier 28 comprising a number of electrodes 30 for monitoringEMG-signals (Electromyography) and/or for providingbio-feedback-signals, e.g. multi-electrodes.

As regards EMG-signals, focus will be placed on the chewing muscles whenbruxism is involved. In technical language, these muscles are calledmuscle Temporalis and muscle Masseter, which can be utilised for theregistration of EMG signals in connection with bruxism.

The Masseter muscle consists of two parts, a surface muscle and adeeper-lying part which, while strongly clenching the teeth, can easilybe localised by pressing a finger into the cheek and leading it out fromthe mouth towards the ear. The main task of the Masseter muscle is toraise the lower jaw, although it also plays a part in the lower jaw'shorizontal movement (as a part of the chewing movement). It contributestowards drawing the lower jaw forwards. Muscle Temporalis is a largefan-shaped muscle which covers and adheres to a large part of the sideof the cranium, which means that most of it is freely accessible.

As mentioned, the muscle activity or the bio-activity is measured bymeans of electrodes, EMG electrodes, placed on the skin over therespective muscles, but other methods can also be used, such asmeasurement by means of sound via contact microphones etc.

In connection with the apparatus shown in FIGS. 1 and 2, the electrodes30 may monitor EMG-signals from the muscle Temporalis. In FIG. 2 onlyone group of electrodes are shown, but evidently another group may besituated at the other side of the housing 12 and/or more than one groupmay be placed at each side of the housing 12. The electrodes areconnected to the circuitry in the housing 12 by means of wires (notshown) that may be in the form of flexible wires, printed wires etc.,and possibly integrated with the strap 14 or designed as an independentpart situated e.g. behind the strap. The strap 14 itself may be designedin various manners, e.g. using flexible material etc. and as a part thatmay be adjusted, removed etc. Further, the apparatus may compriseconnection means (not shown in FIG. 2) for a battery charger and/or adata connection for a PC such as a USB-connector placed in the housing12.

According to an important embodiment of the invention, an individualadjustment to the individual user will be effected, which will beexplained in the following.

Such an individual adjustment may be carried out by making use of anintroductory set-up procedure, after which use may be effected through aset-up period. Hereafter, the apparatus according to an embodiment ofthe invention is adjusted to the user, so that the apparatus can betaken into normal use. However, the apparatus may be taken into usedirectly after the set-up procedure.

Before describing the apparatus shown in FIGS. 1 and 2 in furtherdetail, a typical sequence for a set-up procedure in general inaccordance with the invention will be described in the following withreference to FIG. 3, which shows a flow diagram for a set-up procedure.

If use is made of electrodes, such electrodes are first mounted, e.g.either on Masseter or Temporalis muscles.

Hereafter, a strong muscle activity is measured at 121. The teeth areclenched hard together for a period of for example 10 seconds, wherebyMBF (=the maximum biting force) is determined. Measurement is then madeof a normally-occurring muscle activity. This is effected by twoordinary “grimaces” being made. The grimaces are made naturally withoutexaggerated effort for e.g. 2 seconds. A first grimace is measured at122 and a second grimace is made for e.g. 2 seconds and measured at 123.

Hereafter, at 124 the user can key-in the desired percentage of themaximum MBF, for example in the interval of 3-20%.

On the basis of the maximum biting force and maximum grimace (the muscleactivity measured at one grimace), calculation is made of a thresholdvalue, a TH-value, which can vary from 3 to 20% of MBF.

Minimum TH-value will always be greater than the maximum amplitude ofthe grimaces, i.e., if for example MBF=100 and the maximum amplitude ofthe grimaces=10, the TH-value will be able to be selected from 11 to 20%of MBF. In this way, normal jaw movements will not have any influence onthe detection of bruxism.

Hereafter, at 125 the user can select the duration of the stimulationpulse. A selection from e.g. 0.1 to 0.9 seconds may be made. The desiredstimulation duration, which is used for setting the stimulationintensity, can be keyed-in so that this does not feel unpleasant for thepatient.

At 126 the stimulation delay can be set. The stimulation delay is thetime for which the apparatus measures the grinding of the teeth beforethe arrival of the stimulation pulse. Selection can be made from e.g.0.5 to 5.0 seconds. The desired stimulation delay is keyed-in (timerdefinition, which will increase the certainty in connection with thedetection of bruxism).

Hereafter, the intensity of the stimulation can be tested at 127 beforeuse is made of the apparatus. All the personal parameters have now beenfound and the apparatus will be ready for use and/or data sampling asshown at 128.

An accumulation of data over a suitable period of time may constitute aset-up period for the apparatus, where a collection of data is providedwhich is specific for the user, and which may consequently be used inthe determination of whether or not a feedback is triggered, for examplewith bruxism. Such a set-up period will be described in more detaillater.

The apparatus shown in FIGS. 1 and 2 will now be described in furtherdetail with reference to FIGS. 4 to 7 showing the display means 16 indifferent situations and steps of use and/or setup procedures.

FIG. 4 shows a sequence 16 a to 16 e of the display means during aset-up or learning procedure, e.g. where the user is introduced to theapparatus by a supervisor, e.g. a dentist, at a hospital etc.

First, the apparatus is turned on, e.g. by manipulating one of thebuttons 18. The apparatus indicates that it is turned on by means of theindicator 20, e.g. LED green, and/or by means of the display means 26.It will be understood that the indicator 20 and the display 16 may showthe same information simultaneously, e.g. instructions to the user. Theuser may view the information on the display 16 in a mirror, e.g. whenthe apparatus is worn on the head, but the skilled user may be providedwith the same information when observing the light form the e.g.LED-indicator. As mentioned above the LED may be a three-colour LED, andthe combinations of colours and/or the use of different blinkfrequencies may define specific information. Thus, the skilled user willalso be able to operate the apparatus during the night, if needed, e.g.for adjusting the feedback level.

The apparatus is connected to a PC by means of e.g. a USB connection,and by means of a set-up software application the apparatus is put intoa set-up mode by the supervisor.

The display means 16 shows the picture 16 a in FIG. 4 when ready forset-up. In this picture the battery indicator 24 is also shown, whichwill be part of the other display pictures as well. Automatically or byoperating one of the keys 18 the display means will shift to the picture16 b, indicating that the user can now put the apparatus on, after theconnection to the PC has been removed, and possibly after having applieda contact gel to the electrodes 30, in such a manner that the electrodes30 are located in close proximity to the skin at the muscles located atthe temple, e.g. Muscle Temporalis. The apparatus 10 will monitor theconnectivity of the electrodes to the user, e.g. by outputting a weakcurrent on one (or more) of the electrodes 30 and by measuring theresulting difference in voltage. The result of this, e.g. the resistancebetween electrode(s) and skin, will be shown on the connectivityindicator 26. If the result is insufficient, the user may adjust theapparatus, e.g. adjust the strap 14, the electrode carrier 28 and/or theelectrodes 30 in order to achieve a sufficient connectivity.

When it is registered that the connectivity is adequate, the apparatusautomatically shifts to the next display picture 16 c, showing a maindisplay icon 36 instructing the user to clench the teeth firmly togetherfor a predefined short period of time, and the result, e.g. theamplitude and frequency of the EMG-signals are registered. As shown inFIG. 4 at the display 16 b, the two buttons 18 may have specialfunctions in these situations, e.g. in dependence on the displaypicture, as shown with the symbols 33 and 34, e.g. return to theprevious picture by 33 or acknowledge that the instruction has beenfollowed 34. Similar will apply for the other display pictures in FIGS.4, 5, 6 and 7.

Subsequent to the clenching step, the apparatus may automatically shiftto the next display picture 16 d, instructing the user to performgrimaces as indicated by the icon 38. This may be done by having thesupervisor instructing the user to perform a number of characteristicgrimaces, e.g. in accordance with the above-mentioned softwareapplication, and the results, e.g. the amplitude and frequency of theEMG-signals are registered.

The user is now instructed to shift to the biofeedback adjustment 16 e,e.g. by pressing both buttons 18 simultaneously. Here, the level of thebiofeedback signals, e.g. the electric stimulation signal or signalsapplied to the user via one or more of the electrodes 30 when a bruxismactivity has been detected, is adjusted. This is done by means of thebuttons 18, e.g. by reducing the level by one of the buttons 41 andincreasing the level by the other button 42. As indicated, the level 40of the feedback can be adjusted in steps, e.g. from 1 to 9. Initially,the level is set at the lowest level, and a short pulse with this levelis delivered to the user. Each time the level 40 is altered, a shortpulse with the selected intensity is delivered to the user. When theuser has chosen an intensity level, the set-up procedure is completed,and the user may hand over the apparatus to the supervisor who by meansof the PC puts the apparatus into a user-mode. The measurements and thesettings are stored in the apparatus, e.g. in non-volatile storagemeans, whereby the settings etc. will not be influenced by battery shiftand/or battery charging etc.

The ordinary use, i.e. use of the apparatus in the user-mode isillustrated in FIG. 5. As previously described for the set-up procedurethe apparatus is activated, i.e. turned on by operating one of thebuttons 18, whereby the display means will show the “ready”-picture 16f, including the battery indicator 24. Contact gel can be applied atthis stage or before activating the apparatus. The apparatus willautomatically—or after having manipulated a button 18 again—shift intothe “adjust”-picture 16 g showing the “adjust”-icon 32. The user puts onthe apparatus 10 and adjusts the strap 14 until the electrodes 30 are inclose proximity to the skin and placed at the location of the muscleTemporalis. As described above, the apparatus monitors the connectivityof the electrodes 30 and when the result is found to be adequate (whichis also shown on the connectivity indicator 26), the apparatus shiftsautomatically into the next display image 16 h, whereby the user isinstructed by the “clench”-icon 36 to clench the teeth hard together fora short moment. The apparatus measures the amplitude and frequency ofthe EMG-signal and shifts automatically to the next display picture 16 ithat by means of the icon 44 indicates to the user that he/she may nowgo to sleep.

In a modified embodiment of the invention it may not be necessary toperform a measuring of the clenching in the use-mode, e.g. the apparatuswill be able to perform automatically. Thus the step relating to themeasuring of the clenching, e.g. related to the display image 16 h, willnot form part of the procedure in the use-mode environment, but onlyduring the supervised set-up procedure.

For both of these embodiments the apparatus will hereafter monitor theuser on the basis of the EMG-signals from the user and if a bruxismactivity is detected on the basis of the settings and parameters alreadyregistered, a biofeedback signal is delivered to the user. In this modethe display 16 will be turned off after a predetermined time ofinactivity, i.e. a period of time, in which the buttons have not beenmanipulated. However, the user may at any time, e.g. during the night,adjust the biofeedback level by operating both buttons 18 simultaneouslyas previously described, whereby the display image 16 j will emerge andthe intensity level may be reduced (41) or increased (42).

When the user wakes up again, e.g. next morning, and takes the apparatusoff, the display means will be turned on again automatically, and theuser may now use the two buttons 18 to display information regarding thelapsed sleep session and information regarding the lapsed session inrelation to earlier sessions, e.g. in order to illustrate anydevelopment. This is shown in FIG. 6, where the first display image 16 kshows a number indicated by 45, e.g. a “magic” number or a performancenumber which indicates an overall grind (or bruxis) activity. Thisnumber may be calculated on the basis of the number of grind or bruxismactivities or events during the night (or session), the accumulated ortotal grind time, the intensity of each of the grind events etc. inrelation to the lapsed time during the session and on the basis of analgorithm or the like. The overall grind activity may thus beillustrated by a “magic” number or a performance number between 0 and99, where the number 0 is designated as the lowest grind activity.Further, in this display image a graphic overview 46 of the grindactivities or events during the preceding sessions or nights, forexample the preceding 7 nights are shown, for example in the form of abar graph 46. In this manner the user may immediately review thedevelopment, e.g. improvement in the grind activity. If for some reasonthe information related to a session cannot be used, e.g. if theelectrode connectivity has been below the required level or if thebattery level has been inadequate, the bar in question may be shown withe.g. a different colour or pattern to indicate that this particular barshould be omitted when assessing the result.

The next display image 16 l shows the total lapsed time 48 during asession, e.g. a night's sleep. The last display image 16 m in FIG. 6shows the number 50 of occasions during a session that a grind orbruxism activity has been detected.

In FIG. 7 a number of further display images are shown. The displayimage 16 n shows that the battery in the apparatus is being charged asalso indicated by the battery indicator 24. Further, the icon 52indicates to the user that the apparatus cannot be used. The imagedisplay 16 o indicates to the user that the battery now is fully chargedand that the charge connection may be removed. The image display 16 pindicates that the apparatus is connected to a PC, e.g. for transferringof accumulated measured and registered data to the PC for processingand/or transmission to a supervisor, a dentist etc., and that theapparatus cannot be used as indicated by the icon 52. Further, the imagedisplays 16 q and 16 r shows two fault situations that might arise andrender the data stemming from a session unsuitable for statistical useetc. The image display shown as 16 q indicates that the battery has notsufficient charge capacity left for a session, e.g. an 8 hour session.The last of the image displays 16 r indicates that the electrodeconnectivity has been below standard for a predetermined accumulatedperiod of time, thereby rendering the results achieved during a sessionunsuitable for further processing, statistical use, etc.

In this connection it is noted that information to the user shown on thedisplay, e.g. warnings regarding battery charge, electrode connectivityetc. is also provided to the user by means of the indicator 20. This maytake place by having the indicator 20 take different colours, e.g. threedifferent colours and combinations hereof, and by having the indicatorbe lit continuously or blink with different blink frequencies.

In FIG. 8 a general overview of an apparatus as described above has beenshown in block diagram for, e.g. showing the main components of such anapparatus. Thus, the housing 12 is illustrated comprising amicroprocessor 60 for processing signals, storing settings, data etc.and facilitating transmission of biofeedback signals etc. Further, thehousing 12 comprises the main display means 22 and an energy supplysource in the form of a battery 61. As already described the housing 12has a number of buttons or keys 18, a visual indicator 20 in the form ofe.g. a LED and a plug-in connector 62, e.g. a USB connector or the like.This connector 62 may be connected to a PC or the like 64 by means of aconnector plug 65, e.g. for setting up the apparatus or for transmittingdata to the PC, from which it may be transmitted to a supervisor, e.g. adentist or a medically trained person. Further, the same connector 62may facilitate a charging of the battery 61 since a plug connector 67from a charger 66 may be connected.

Further, it is shown in FIG. 8 that an electrode assembly or carrier 30comprising a number of electrodes 28 is connected to the apparatus bymeans of wires 29. This assembly may be situated to the right or to theleft. In either case the monitoring will be performed on the muscleTemporalis. Additionally, a further set of electrodes 28′ carried by acarrier 30′ and wires 29′ may be connected to the apparatus, e.g. formonitoring muscle Temporalis at the other side of the housing. In mostcases a single electrode assembly will suffice, but in some casesbruxism may be located at one side only or the bruxism events may differfrom one side to the other.

FIG. 9 illustrates a system in accordance with a further embodiment ofthe invention in block diagram form, e.g. an anti bruxism module systemABM system. Here an end-user 70 and a supervisor 71 are shown in thelower level. Above these there is shown the hardware level HW and in theupper half of the figure the software level SW. EMG-measurements fromthe end-user 70 is performed via an AD-converter 72, from which thesignals are delivered to a measure block 75. The registered signals areused in three types of processing: for evaluating in accordance with amaximum force calculation 76, for evaluating in accordance with an areacalculation 77 and for evaluating in accordance with a FFT-processing(Fast Fourier Transform) 78. These will be described in further detailbelow. The output from these three evaluations are provided to theapplication logic 79, where it is evaluated whether a feedback should betriggered or not in accordance with the setting that has been performedvia the setup-part 81. If a feedback signal is to be delivered, this isdelivered via a feedback part 80 to a stimuli interface 73 and to theend-user 70. Further FIG. 9 illustrates the electrode monitoring that isperformed via a part 82 that sends a signal with a small amplitude and apredefined frequency to the end-user via a DA-converter 83. This signalis measured via the blocks 72, 75 and 78, where it is recognized by thepredefined frequency, whereby the electrode monitor block 82 mayevaluate the electrode connectivity. This and other information may beshown on the display 92 and/or indicated by means of the opticalindicator 91, e.g. a LED indicator. It is noted that any informationthat is needed for operating the apparatus may be provided to the userby means of the display 92 as well as by means of the LED indicator 91as previously described.

As also previously described the setup of the system may be performedusing a PC communication 84 that also may serve to download data fromthe apparatus, e.g. via a USB driver 89 and a USB connection 90 to a PCat e.g. the supervisor 71. Further, a display driver 85 for operatingthe display 74 and/or the LED indicator 91 is shown and a block forperforming a dump 86 of data via a flash-driver 87 to storage means inthe form of e.g. a flash memory 88 is also shown.

For further exemplification of the invention and various embodiments, ablock diagram in FIG. 10 shows signal processing methods according tothe invention. The raw data recorded from microphones, electrodes orwith other means 301 is sent to a microprocessor for a further analysisof the signal as follows:

At 302: The signal is amplified (possibly 0-5V) and is then sent to anADC (possibly 12-bit, 5V=4096).

At 303: All DC is removed, i.e. the average value is calculated, so thatthe signal will lie symmetrically around the 0 point (±2.5V=±2048).

Hereafter, the following signal processings are possible, namely:

1) One can select to make an RMS calculation of the signal, where theresult is compared with a predetermined table which contains referencefrequencies (determined during the set-up period) from the patient'socclusion reliefs during bruxism. I.e. if a frequency pattern (or more)can be recognised from the table during the continuous accumulation ofdata from the patient, the feedback (stimulation) will be activated.

This takes place as shown in FIG. 10.

At 304: The signal is filtered in a band-pass filter.

At 305: The RMS value is calculated.

2) The RMS determination is effected followed by an integrator, wherebythe certainty with regard to detection of bruxism will be furtherincreased.

Otherwise the same method as described under 1) is used.

At 306: The signal is integrated.

At 307: The RMS value is calculated.

3) An even more secure method for the detection of bruxism is that ofcarrying out an FFT (Fast Fourier Transform) analysis of the signal, asdescribed in the following:

When the average value of the signal is determined at 303, the signal issent to a low-pass filter 308 where all noise and unusable signals arefiltered out. Thereafter, the signal will be averaged and rectified, 309and 310; and an FFT analysis is effected at 311 so that the frequencycontent of the signal is determined. In this way, which frequencies arecollected in the system can be ascertained with high certainty.Thereafter, a Pattern Recognition of the signal must be carried out at312.

The principle is that there is first carried out a so-called Peakdetection, where on the basis of the FFT analysis and the foldingprinciple the highest peak value (amplitude value) is found, such as isillustrated in FIG. 11.

This means that a folding of the signal is effected, where one can findout how the signals with the given frequency content lie in relation toone another. It is ascertained which frequencies lie closest to thefrequency 1, which in this case are the frequencies 2 and 3.

The method is a stochastic signal processing where the patient mustfirst use the apparatus for a period (approx. 7 nights) withoutactivation of the feedback. This is an individual adjustment where itmust be registered which frequency patterns are formed when the patientgrinds his/her teeth (with regard to determination of the frequencypatterns, reference is made to the article Lavigne G J et al (1996), JDent Res 75(1): pp. 546-552, possible frequency patterns phasic, tonic,and mixed). When these frequency patterns are determined, they arecollected in a table and stored in a memory which is accessible for themicroprocessor.

With the registration of bruxism via the apparatus such as shown in FIG.10, a correlation can be ascertained between the frequency content ofthe signal from the continuous measurements (recorded from themicrophones/sensors, 301) and the recorded signals which lie in thetable. After this registration, the following must be carried out:

-   -   One first looks at the 1^(st) harmonic frequency (1 in FIG. 11).    -   If there is a match, a look is taken at the 2^(nd) and 3^(rd)        harmonic frequency (2 and 3 in FIG. 11). In order to further        increase the certainty, a look can also possibly be taken at the        4^(th), 5^(th), 6^(th) harmonic frequencies if this is        necessary. However, as a rule it is not necessary to go so high        up in harmonic frequencies for detection of bruxism.

I.e. when these harmonic frequencies match the frequency content of thesignals from the table (stored in the memory), it can with certainty beascertained that the patient is grinding his/her teeth (bruxism), andthe feedback may necessarily be activated.

In this manner, the certainty with regard to the detection of buxismwill be very great (close to 100%), so that the patient does not getpunished for normal teeth-clenching activity during sleep.

The difference between this method and all the other existing methods isthat this apparatus focuses only on the detection and herewith thetreatment of bruxism, where all the normal biting activites, possibleexternal disturbances/sources etc. are eliminated.

As mentioned earlier, an accumulation of data etc. is carried out duringa set-up period which will be described in more detail in the following.During this set-up period, the apparatus is set individually where, forexample, the patient can use the apparatus for a min. of 7 nights insuccession, without activation of the feedback. In this way, all thepersonal parameters related to bruxism are registered and stored in atable (personal table), which during the signal processing will be usedfor pattern recognition as shown at 312 in FIG. 10. The apparatus can beconfigured and set in such a manner that the feedback can be activatedonly when the threshold value is exceeded, and as a minimum the 1^(st)harmonic frequency, cf. FIG. 11, matches one of the frequencies whichlie in the table.

According to a further embodiment of the invention, it is taken intoaccount that the stimulation shall be able to be adjusted individually.For example, on the basis of the table it can be ascertained whichfeedback fits the patient's bruxism pattern, where the feedback (thestimulation) is set regarding duration, intensity and delay. This meansthat if the patient has a tendency to grind teeth e.g. for 3 seconds andthen cease grinding for up to 1-2 minutes, and thereafter repeats thisteeth-grinding pattern in this periodic manner, a stimulation with ahigher intensity and shorter duration will be required in order tooptimise the efficiency of the feedback. On the other hand, if thepatient grinds the teeth for longer periods with shorter intervals, thenuse must be made of a stimulation which is ramped up with determinedsequencies and longer duration. I.e. in accordance with bruxism patternsdetermined during the set-up period, the feedback will automatically beset/adjusted so that it is most effective for the patient. Thisoptimises the treatment of bruxism. At the same time, importance isattached to the patient not being awakened by the feedback (thestimulation).

Moreover, it should be noted that a further advantageous embodiment ofthe invention comprises a division of the apparatus into a master part,in which the processing of the signal itself is effected, and a slavemodule in which signal recording, possibly digitalisation andtransmission to/from the master module is carried out. Furthermore,feedback can be effected via the slave module or it can be effected viaa separate module.

With this dividing of the apparatus, where the transmission of datatakes place in a chiefly wire-less manner, the weight, extent etc. ofthe slave module or the modules can be minimised so that the user isaware of this to a lesser degree. Moreover, the user can move relativelyunhindered by the slave module.

The processing of the signal in the master module, which for example canbe a microprocessor-equipped apparatus or the like placed in thevicinity of the user, for example at the side of the bed, will now bedescribed in more detail with reference to FIG. 12.

The master module consists of main processor 610 and transmissioninterface 612 to a PC, and a transmission interface 611 to the slavemodule.

The data from the slave module is transmitted to the master module whereall data/signal analysis for the handling of bruxism takes place in themain processor 610. The result of the data analysis (in cases whereperiods of bruxism can be ascertained) is sent back e.g. to the slavemodule via 611, where the bio-feedback is activated, or to a separateexternal module, such as a vibrator module, where bio-feedback iseffected.

All the data is transmitted and stored in the main processor 610, wherevia 612 it is possible to send the data further to a PC.

The processing of the signal in the slave module will now be describedin more detail with reference to FIG. 13.

The signals in the form of sound, muscle movement/contraction and EMGare detected by a sensor 601 (microphone, electrode, piezo-sensor etc.).These signals will be processed in the analogue circuit 602 and are sentfurther to a processor 603.

The digitalised data is transmitted 604 to a stationary main processor(master module, cf. FIG. 12), where the necessary data analysis iscarried out, such as disclosed in the claims and the description.

When the necessary/mentioned criteria for bruxism have been fulfilled, asignal will be sent via 604 to the processor 603, after which abio-feedback signal 605 is activated in the form of sound, vibrationand/or other stimuli, which via 606 is sent to the patient. Thebio-feedback can be entered either in the slave module or into a furtherpart such as a vibrator module, a bracelet vibrator or the like.

In the following, various other embodiments of the invention and theirpractical configuration will be described in more detail with referenceto FIG. 14-20.

A first embodiment of a slave module according to the invention is shownin FIG. 14-16. Here, there is shown an embodiment 400 of the apparatuswhich can easily be placed behind the ear. FIGS. 15 and 16 illustratehow the apparatus shall be used. The signals (generated by grinding ofthe teeth) are detected via a microphone 401, and the feedback in theform of stimulation is connected possibly to the ears by means of theelectrodes 402.

As shown in FIG. 16, the stimulation electrodes 403 can instead beplaced on the masseter muscles.

A second embodiment of a slave module is shown in FIG. 17-20. As shownin FIG. 17, this embodiment of the apparatus 500 (the slave module) isconfigured in such a manner that it resembles a headphone, so that itcan easily be placed either on the patient's head or forehead. Theapparatus is configured as a slave module which can communicate in asubstantially wire-less manner with a master module. This master modulecan comprise the most essential parts of microprocessors, memory unitsetc., so that the slave module needs only to comprise atransmitter/receiver, and circuits which are necessary for the leadingof signals to/from electrodes, sensors and/or transducers.

The EMG signals from the masseter muscles are detected via theelectrodes 501 and processed in the slave module 500. The bio-feedbackin the form of stimulation is connected to the same electrodes 501. Theelectrodes 501 are used for both detection and stimulation.

Instead of the electrodes 501, there can possibly be connected anintegrated system 502 which contains both a microphone 503 and aloudspeaker 504 on the apparatus. The microphone is used for thedetection of frequencies generated by bruxism, and the loudspeaker 504is used to send the bio-feedback to the patient in the form ofsound/frequency. The principle is illustrated in FIG. 19.

The electrodes for the detection of EMG activities can possibly beplaced on temporalis muscles as shown in FIGS. 20 and 21, where thebio-feedback, e.g. in the form of a vibrator 505, can possibly be placedon the patient's arm in the form of a bracelet vibrator, such asillustrated in FIG. 22.

The slave module 500 and the bracelet vibrator 505 can preferablycommunicate in a wire-less manner (separate) with the master module.

The vibrator 505 shall only receive signals (only RX) from the mastermodule, which is described in connection with FIG. 12, where thebio-feedback in the form of vibration is activated when bruxism isdetected from the slave module 500.

When the necessary/mentioned criteria for bruxism have been fulfilled, asignal will be sent from the master module (as shown in FIG. 12) to thevibrator 505, where a bio-feedback signal is activated in the form ofvibration. The signal processing for this function appears from FIG. 23.

When, for example, the apparatus is used in the combination as shown inthe FIGS. 20 and 21, the biofeedback part 605 and 606 can possibly beplaced in the bracelet vibrator 505.

The data analysis and the processing in the PC will now be described inmore detail with reference to FIG. 24.

All data which is stored in the master module can be transferred to a PCvia 612 for a further analysis of the processing period. A programme 624which can receive the data is installed on a PC 623. In the programme624, all data from the patient (for each night) is processedsystematically to determine the efficiency of the processing period. Inthis way the patient himself can follow the course of events. Thepatient can possibly send the data further to his doctor/dentist via theprogramme interface 625, which can establish connection to the Internet.

A still further example of an embodiment of an apparatus in practicewill be explained with reference to FIG. 25, which shows such anapparatus in block-diagram form. By means of the apparatus, it ispossible to stimulate the jaw muscle of people who are in the habit ofgrinding their teeth, so that the jaw muscle is relaxed and thedisturbing teeth grinding/bruxism is avoided.

The signals from the electrodes 101 are sent via the analogue switch 102to the EMG signal processing part 103.

In a preferred embodiment, use is made of so-called multi-electrodeswhich can be used both to stimulate a muscle and to register themuscle's activity. The multi-electrode's function, respectively totransmit or register signals, is controlled by an analogue switch 102from the microprocessor 106.

Analogue signal processing is carried out in 103, where thebio-potentials recorded from the electrodes 101 are amplified, filteredand rectified, so that the processor 106 can be utilised to the bestpossible degree.

The signals from both electrodes 101 are sent to the microprocessor 106,where communication between the microprocessor 106 and connectedcircuits takes place via a bus system.

The task of the microprocessor is to carry out the signal processing ofthe EMG sampled by the analogue-to-digital converter and possible EEGsignal, and to manage the communication with the user interface.

Registered and processed data can be communicated to a PC or other dataprocessing system, for example in accordance with the RS-232C or USBstandard. This communication takes place via the gate 107.

The biofeedback circuit 108, which in this case is in the form of astimulation influence, is controlled by the microprocessor 106, where itis possible to adjust/set the intensity of the current transmitted.

In a preferred embodiment of the apparatus, the stimulation signal istransmitted through the same multi-electrode as that which collects themuscle activity signal.

The circuit 109 shows a block diagram for a preferred embodiment for theprocessing of the EEG signal.

Signals which represent the activities which take place in the brain canbe registered from the surface of the cranium. The electrical signal inthe form of EEG is registered with the electrodes 104. Electricalactivities recorded from the brain by the electrodes have a very lowamplitude, max. 20μ-200μ Volt. The signals from the electrodes 104 aresent to the EEG signal processing part 105.

The information which is desired to be processed with the apparatus liesin the EEG signals, which are registered with the electrodes 104 in afrequency range between 0.5 and 80 Hz. The analogue signal processingpart on EEG potentials takes place in 105, where the signal is processedso that the useful frequencies are amplified, filtered and rectified.The signals from the EEG electrodes 104 are sent to the microprocessor106, where a processing of the EEG signal sampled by theanalogue-to-digital converter is carried out. Data for the relevantparameters (frequency, amplitude, the RMS value), which are indicativeof the sleep stage 2, are placed as reference in the microprocessor(106).

In an alternative embodiment of the apparatus, each of the signals fromthe right/left side of the jaw can be processed independently, and twoindependent stimulation signals can be sent out on each side of the jawrespectively, whereby it is achieved that bruxism which occurs only atthe one side or the other side can be processed independently.

FIG. 26 shows a first signal which represents muscle activity as afunction of time, where various forms of muscle activity occur. Thelevel for the threshold value Th mentioned earlier is indicated by ahorizontal line at 36.0 microvolts. The signal comprises a number ofcharacteristic signal sequences 1, 2, 3 and 4. The signal sequences 1represent ordinary swallowing movements. The signal sequences 2represent the muscle activity with speech and laughter. In thesesituations, no form of stimulation shall be triggered.

The signal sequences 3 represent ordinary teeth-clenching activityduring sleep. This increased muscle activity will typically be relatedto dreaming by the patient. Despite the fact that the muscle activityexceeds the threshold value Th, no form of stimulation shall betriggered, as this muscle activity is not harmful to the teeth norcauses any pain due to the increased muscle activity. According to theinvention, this decision can be made on the basis that the muscleactivity only exceeds the threshold value for a limited interval oftime, e.g. less than 5 seconds.

On the other hand, the signal sequence 4 represents biting activityduring sleep which may be considered to be bruxism. This increasedmuscle activity has a somewhat longer duration than the signal sequences3. It has been ascertained in practice that ordinary clenching andmuscle activity can be distinguished from real bruxism by monitoring theactivity level over a period of approx. 5 seconds, where the activitylevel exceeds the threshold value. If the activity level after thisperiod still exceeds the threshold value, a stimulation signal istriggered so that the jaw muscle is relaxed and the bruxism is herewithterminated.

The period for which the activity level shall exceed the threshold valueto bring about the triggering of a stimulation signal can be selected inan interval from approx. 2-4 seconds and up to 8-12 seconds, which canbe done during the set-up procedure.

FIG. 27 shows a second signal which represents the muscle activity as afunction of time. This shows how biopotential signals which are recordedfrom the masseter muscles are divided into windows with a time intervalof, for example, 500 ms. During each time interval (500 ms), acalculation is made of the area below the curve and of the RMS value.These signals can be stored in memory for later analysis of the muscleactivity.

FIG. 28 shows a third signal which represents the muscle activity as afunction of time. In a preferred embodiment, a calculation is made onlyof the area and RMS values for the sequences of the EMG signals whichlie above the level of the threshold value and which, for example, lastlonger than 5 seconds.

FIG. 29 shows the area below the maximum biting force, which iscalculated in the microprocessor 121.

As discussed earlier in the description of the set-up process, ameasurement must be made of the maximum biting force in the form of theEMG signals which are used to determine the threshold value, MBF(Maximum Biting Force). The threshold value typically lies in the regionbetween 3 and 20% of the maximum force (MBF).

For the determination of the threshold value during the set-upprocedure, the electrodes 101 and 104 must be mounted on the massetermuscles, and the user shall clench the teeth strongly together for 2-5seconds. Thereafter, the apparatus must be adjusted to a certain % MBF,which can vary from 3 to 20% of MBF, corresponding to a desiredthreshold value.

On the basis of the threshold value found, the microcomputer 106calculates an area value which determines when the stimulation shall betriggered. The area value is used as a form of reference and correspondsto that area which appears when the amplitude of an EMG signal hasexceeded the threshold value for more than, for example, 5 seconds, suchas keyed-in during the set-up procedure.

In order to stimulate the masseter muscles when the selected thresholdvalue is exceeded, the potential on the output from the microcomputermust be converted to current. Since it cannot be known beforehand howmuch current shall be transmitted to the patient, so that a painthreshold is not exceeded, there must be a possibility of adjustment ofthe intensity of the current transmitted, which can be effected inseveral ways, as will be well-known by those skilled in the art.

FIG. 30 shows a block diagram for a preferred embodiment for the EEGsignal processing. By means of EEG signal processing, it is possible toregister/analyse the stages of sleep, which in professional language iscalled REM sleep (Rapid Eye Movement sleep). The sleep is divided intothe stages REM 1-4, where REM1 is defined as that stage at which aperson has just fallen asleep, and REM4 as the stage of deepest sleep.

As mentioned earlier, bruxism occurs mostly in sleep stage 2 and duringawakening.

In the apparatus it is possible to analyse the EEG signals incombination with EMG-signal processing, so that the periods of bruxismcan be analysed in various stages of sleep. Moreover, the apparatus canbe set so that the stimulation is triggered only when the patient is insleep stage 2.

Electric signals which represent the activities which occur in the braincan be registered from the surface of the cranium. The electric signalsare registered with the EEG electrodes 701 and 703 (where 702 is used asreference). The electrodes are used for the measurement of electricalactivities in the form of EEG signals, and they are placed on theforehead over the eye.

The signals from the electrodes 701 and 703 are sent to respective EEGamplifiers 704 and 705. The amplifiers 704 and 705 are instrumentationamplifiers which have very high input impedance and are good atsuppressing so-called common-mode voltages. The amplified signals fromthe amplifiers 704 and 705 are filtered by means of the band-passfilters 706 and 707, herewith increasing the signals' signal/noiseratio. The information which is desired to be processed by the apparatuslies in the EEG signals, which are registered with the electrodes 701and 703 in a frequency range between 0.5 and 80 Hz. The band-passfilters 706 and 707 therefore have lower and upper −3 dB limitfrequencies of 0.5 Hz and 80 Hz respectively. The stop band herewithcomprises frequencies lower than 0.5 Hz and frequencies higher than 80Hz. The signals from the band-pass filters 706 and 707 are rectified bymeans of the rectification circuit 708 and 709, so that the voltage spanfrom a unipolar voltage (±) is converted to a positive voltage.

The signals from the rectification circuit 708 and 709 are amplified inthe amplification circuit 710 and 711, so that the microprocessor 106and a built-in analogue-to-digital converter can be utilised to the bestpossible extent.

The signals from the EEG electrodes 701 and 703 are sent to themicroprocessor 106, where a processing takes place of the EEG signalsampled by the analogue-to-digital converter. Data for the relevantparameters (frequency, amplitude, RMS value), which are indicative forsleep stage 2), are placed as a programme in the microcomputer 106.

When the user falls asleep, the sleep stages will be scanned, forexample every 1 second, and the EEG signals are continuously comparedwith the parameters which correspond to the brain activities which occurin sleep stage 2. These signals are of different amplitudes andfrequency, depending on the sleep stages 1-4, and in this manner themicrocomputer can recognise the signal/frequency of the relevant sleepstage (in this case sleep stage 2).

For the determination of the sleep stages, use will typically be made of2 concepts, namely amplitude of EEG signals and frequency of EEGsignals.

In the apparatus there is the possibility of analysing the EEG signals(a method for the analysis of the brain's electrical activities andregistration of the sleep stages) in combination with EMG signalprocessing, so that the periods of bruxism can be analysed in differentstages of sleep.

In the stages of lighter sleep a general increase in the muscle activitycan be observed in relation to the deeper sleep. Bruxism thus occursmainly in sleep stage 2 and during awakening. But in the stages ofdeeper sleep there can occur some ordinary teeth-clenching activity,which with an EMG registration alone can be difficult to distinguishfrom bruxism. When this is combined with a system for the determinationof the sleep stages, the certainty in the detection of nightly bruxismwill be far greater.

Therefore, the patient must use the apparatus for a minimum of 7 nightswithout activation of the feedback (the set-up period), wheresignals/frequencies from both EMG and EEG measurements are stored in amemory. Thereafter, an analysis is made of the correlation between EEG(sleep stages) and EMG (teeth clenching activity in the masseter ortemporalis muscles), where the result will be used for the detection ofbruxism and herewith activation of the feedback. In this way theapparatus is able to be adjusted individually.

In the microprocessor, continuous analysis is made of signals from boththe EMG and EEG electrodes, for example every half a second. Thesevalues are compared periodically with the reference values, for examplein the form of an individual table which is defined during the set-upperiod, and when there is agreement between these values, themicroprocessor will indicate with great certainty that the user isgrinding his/her teeth. In this manner the certainty is greatlyincreased with regard to the triggering of stimulation, so that thenormal teeth-clenching activity or a sudden spike which exceeds thethreshold value will not give rise to a triggering of the feedback (thestimulation).

When this method is used for the detection of bruxism, the processing ofthe EMG signal will be able to be digitalised to a greater degree.

The patient shall merely go through the set-up period, which asmentioned as an example can extend over 7 nights or another suitableperiod.

FIG. 31 shows a routing diagram for the measurement of the muscleactivity and triggering of a stimulation signal. This routing diagramcan be implemented as a programme for the microprocessor 106.

In the first stage 201 in the routing diagram, the patient must gothrough the set-up procedure (as described in connection with e.g. FIG.3) in order to register the personal parameters in the form of MBF(maximum biting force), amplitude of the grimaces, stimulationdelay/duration and threshold value (Th) in the apparatus. The area belowthe signal is calculated and, on the basis of the percentage, athreshold value Th will be calculated in the microprocessor 106 for thelevel of muscle activity which is required to trigger a stimulation.

Alternatively, this threshold value can be calculated automaticallybased on measurements of the muscle activity, or retrieved from a memoryin which the threshold value has been stored earlier.

In stage 202 it is defined whether an analysis of the sleep stages is tobe carried out in combination with the EMG signal processing.

In stage 203 it is presupposed that the earlier-mentioned EEG electrodes104 are mounted on the surface of the patient's cranium, and information(frequency and amplitude) can thus be registered concerning the sleepstages in the form of sample S.

In stage 204 it is presupposed that the earlier-mentioned electrodes 101are mounted on the jaw of a patient, and information concerning themuscle activity can thus be registered in the form of samples S. Themuscle activity is registered in 205, where calculations are made of thearea, max. amplitude and RMS value for a time interval of, for example,500 ms. After stage 205 there follows a loop in the routing diagram.

In stage 213 the timer T is set/reset to zero. In stage 216 it isdecided whether the amplitude/the area of registered samples S exceedsthe max. value of the grimaces (determined during the set-up procedure).If the threshold value is exceeded, it is decided whether theamplitude/the area of registered samples S exceeds the threshold valueTh in 206. If the threshold value is exceeded, the timer is set to zeroin stage 207 or new samples are merely registered in stage 204. Thetimer T in stage 212 is started and new samples S are registered instage 211.

In stage 209 it is decided whether the muscle activity in the form ofthe amplitude/area of registered samples has exceeded the thresholdvalue Th more than the stimulation delay (determined during the set-upprocedure).

In stage 215 it is examined whether analysis of the sleep stages hasbeen desired or not. If this is the case, the EEG signals will becontinuously compared with the parameters for sleep stage 2 in stage214. Data for the relevant parameters (frequency, amplitude) which areindicative for sleep stage 2 are placed as a programme in themicroprocessor 106.

If an analysis of the sleep stages is desired (EEG), the stimulationwill not be triggered until the amplitude of the EMG signals hasexceeded the threshold value by more than the stimulation delay at thesame time that the patient is in sleep stage 2.

In stage 210 a stimulation is triggered in the form of a stimulationsignal which is applied to the patient's jaw through one or both of theearlier-mentioned electrodes. Alternatively, if less time has elapsedthan the stimulation delay while the threshold value has been exceeded,no stimulation signal is triggered. It is hereby achieved that nostimulation signal is triggered before it has been verified that thereis a situation in which real bruxism is present. In this way, ill-timedstimulations of the jaw muscles are avoided.

The shown routing diagram can be implemented so that two independentsignal paths, one for each side of the jaw, can be processedindependently.

FIG. 32 shows an example of a stimulation signal. The stimulation signalconsists of a pulse train where a positive pulse is followed by aninterval of time until a negative pulse arrives. The shape of thestimulation signal is generated by the microprocessor 106. Theparameters which describe the signal comprise the pulse length of thepositive and the negative pulses Tp and Tn respectively, the interval oftime between the two pulses, Tip, the repetition frequency, 1/Ts, andthe amplitude I of the pulses.

In a preferred embodiment, the strength of the current or the amplitudeI of the pulses is varied during a processing. Before processingcommences, a minimum and a maximum amplitude for the stimulation signalis specified. When and if bruxism is detected, i.e. the threshold valueTh is exceeded for more than the stimulation delay, a stimulation signalshall be triggered. The stimulation signal has a minimum amplitude asstart value. If this minimum amplitude is sufficient to terminate thebruxism state, the amplitude of the stimulation signal is held at thislevel. Alternatively, if the minimum amplitude is not sufficient toterminate the bruxism state, the amplitude is gradually increased at acertain rate until the bruxism state can be terminated by stimulation ofthe jaw muscle. However, the amplitude is not increased above thespecified maximum amplitude.

The rate at which the amplitude is allowed to be increased is alsocalled a “slew-rate”. It is also possible to specify maximum and minimumvalues for this “slew-rate”. By ramping the amplitude of the stimulationsignal up or down in this manner, it is achieved that use is made ofthat intensity which is precisely sufficient to terminate the bruxismstate. This is expedient since that stimulation amplitude which isnecessary varies from patient to patient, just as that stimulationamplitude which is necessary can vary over time for the same patient.

Moreover, controlled by an analogue switch from the microprocessor, usecan be made of so-called multi-electrodes which can be used both for thestimulation of a muscle as well to register the muscle's activity.

In FIG. 33 is shown an embodiment of an Anti-Bruxism Module 900, wherethis embodiment of the apparatus shall be placed around the neck, andwhere the EMG electrodes 902 can be mounted on the jaw muscles and/or onthe forehead (above the eyes). Furthermore, there can be the possibilityof the connection of EEG electrodes is this is desired.

FIG. 34 shows an enlarged illustration of a corresponding module 900,where plug connections 904 for EEG electrodes are illustrated. As willbe seen, the EMG electrodes 902 are configured as multi-electrodes, andthe figure also shows that the module comprises batteries in batterycompartments 906 for operation of the signal recording, digitalisation,transmission and operation during set-up procedures etc. It is alsoshown that the module has a display 910 and pushbuttons or the like912-918 for use in the keying-in during the set-up procedure, forexample in the selection of the level of stimuli, for keying-in thedesired threshold level etc.

In the above, the invention has been explained in detail with referenceto specific embodiments and as illustrated in the drawings. As it willobvious to the skilled person, the invention may be performed in manyother forms and variations and should not be limited to the examples ofthe invention illustrated above. The scope of the invention will bedefined by the claims.

The invention claimed is:
 1. An apparatus for detecting bruxism andproviding feedback to a user, said apparatus comprising: a sensor systemoperable to measure the muscular activity of a user's jaw associatedwith a level of biting force and generate a signal correspondingthereto; a signal processor which is in communication with said sensorsystem and is operable to receive said signal as a function of time,wherein said signal processor is configured such that the signalreceived from the sensor system as a function of time is divided intowindows of a predefined time interval and configured such that acalculation of the area under the curve of the muscular activity vs.time is provided for each time window to yield the total biting powerfor each time window and calculate a level of muscular activity andintegrate said level vs. time, so as to provide a processed signal, anda feedback signal generator which is in communication with said signalprocessor, said feedback signal generator being operable to receive saidprocessed signal from said sensor system and generate a feedback signal,and direct said feedback signal to said user if the level of muscularactivity measured by said sensor system exceeds a predefined thresholdlevel of muscular activity for a predefined period of time.
 2. Theapparatus of claim 1, wherein said feedback signal is provided on thebasis of an evaluation comprising an area calculation.
 3. The apparatusof claim 1, wherein said apparatus is configured such that said totalbiting power of each time window is stored.
 4. The apparatus of claim 1,wherein said sensor system comprises one or more electrodes for sensingof EMG-signals.
 5. The apparatus of claim 1, wherein said signalprocessor is operable to calculate a threshold level of muscularactivity which is in the range of 3-20% of a level of muscular activitywhich is associated with a maximum level of biting force.
 6. Theapparatus claim 1, wherein said feedback signal generator includes acontrol system for controlling the duration and/or intensity of saidfeedback signal.
 7. The apparatus of claim 1, wherein said sensor systemis operable to detect EMG signals.
 8. The apparatus of claim 1, whereinsaid apparatus is operable to store data derived from said sensor systemand/or said signal processor and/or said feedback signal generator. 9.The apparatus of claim 8, further including a computer and a system fortransferring said stored data thereto.
 10. The apparatus of claim 1,further comprising a user module configured to be worn on a user's head.11. The apparatus of claim 1, further comprising a display deviceoperable to display information and/or results derived from said sensorsystem and/or said signal processor and/or said threshold signalgenerator.
 12. The apparatus of claim 1, wherein said apparatus isoperable to store said threshold level of muscular activity in anassociated, non-transitory memory.
 13. The apparatus of claim 1, whereinsaid signal processor is operable to accumulate data and determine andstore frequency patterns corresponding to muscular activity and relatingto bruxism.
 14. The apparatus of claim 1, wherein said apparatus isconfigured to be individually adaptable by having adjustment means foradjusting the level of said feedback signal.